GB2182287A

GB2182287A - Paper feeding mechanism for a printer

Info

Publication number: GB2182287A
Application number: GB08625554A
Authority: GB
Inventors: Akio Tajima
Original assignee: Seikosha KK
Current assignee: Seikosha KK
Priority date: 1985-10-30
Filing date: 1986-10-24
Publication date: 1987-05-13
Also published as: DE3636814A1; FR2589454B1; JPS62103169A; KR890003073B1; IN165068B; DE3636814C2; US4688958A; FR2589454A1; GB8625554D0; HK89892A; JPH047911B2; MX160973A; GB2182287B; KR870003873A

Description

1 GB 2 182 287 A 1

SPECIFICATION

Paperfeeding mechanism for a printer h.

This invention relatesto paperfeeding mechanisms for printers.

Conventionally, large size printers provided with automatic paper loading mechanism have been used as outputdevices of word processors, etc. In such an automatic paper loading mechanism, a paper pressing roller is separated from a platen bya manually operable lever projecting outwards, and then a push-button is depressed to start a paper feeding motor so that recording paper is automatically drawn in.

One known frictional paper feeding mechanism is such thata spring fixedto aframe of a printer holds a pinch roller. Alternatively a pinch roller is pressed by a spring attached to a bottom plate of a printer.

In such automatic paper loading mechanisms, operation iscomplicated because both the operation of the manually operable lever and the pushbutton are required. Further, in the above paperfeeding mechanism, when recording paper is inserted as well as fed, the resilientforce by which the pinch roller is urged against the platen is always so strong thatthe recording paper is not easily inserted between the platen and the pinch roller even when the leading edge of the recording paper has come into contactwith the pinch roller. Further, when the recording paper isfed by,forexample, a pin tractor, it is necessaryto provide a separate mechanism for causing the pinch rollerto move awayfrom the platen againstthe spring force resulting in a complicated structure.

The present invention seeksto provide a paper feeding mechanism for a printer in which (a) recording paper can be automatically drawn in by a simple operation, (b) recording paper can be surely inserted between a platen and a pinch roller, (c) misinsertion of recording paper can be easily correctedJor example, in the case wherethe recording paper is drawn in atan angle, and (d) an appropriate tensileforce can be applied tothe recording paper even in the case of tractorfeeding.

Although the present invention is primarily directed to any novel integer orstep, orcombination of integers or steps, herein disclosed and/or as shown in the accompanying drawings, nevertheless, according to one particular aspect of the present invention to which, however, the invention is in no way restricted, there is provided a paperfeeding mechanism for a printer comprising: a platen for feeding recording paper; a pinch roller resiliently urged into contactwith said platen; a platen bearing for rotatably supporting said platen, said platen bearing being arranged to be rotatable by a knob fixed to a outward projecting end of said platen bearing; a cam portion on the platen bearing; a rotatable paper pressing lever supporting a paper pressing rol [er; a connecting leverfor pivoting said paper pressing lever in response to rotation of said cam surface; a cam follower leverfixed on a rotatable support shaft and provided at one end with a cam follower engageable with a cam surface of said cam portion; a support arm fixed on said support shaft so as to be pivotally displaced in response to rotation of said support shaft; a roller receiver carrying said pinch roller at one end thereof; connecting means for rotatably and movably connecting one end of said support arm and the other end of said roller receiver; a spring extending between said support arm and said roller receiver; and a protrusion and a protrusion receiver provided on one and the otherof said support arm and said roller receiver, said protrusion and said protrusion receiver being disposed at a position separated from a line of action of a spring force of said spring, said cam surface of said cam portion including a first, a second and a third positioning cam surface portions of different radii, said first, second and third positioning cam surface portions being, in operation, selectively followed by said cam followerfor displacing said cam follower lever into a selected one of three rotational positions, said cam surfacefurther including a switch pressing cam surface portion for operating a switch controlling a paperfeeding motor.

In the preferred embodiment said protrusion is provided on the support arm and the protrusion receiver is provided on the roller receiver.

Preferablythe spring extending between said support arm and said roller receiver is a tension spring.

Accordingly, on insertion of recording paper, merely by operation of the knob, the cam portion is rotated to cause the paper pressing rollerto separate from the platen, and atthe same time the cam follower moves from the first positioning cam su rface portion to the second positioning cam su rface portion thereby to actuate the switch controlling the paperfeeding motor. If the knob is turned further,the cam follower movesfrom the second positioning cam surface portion to thethird positioning cam surface portion, so thatthe support arm is pivoted and thefulcrum defined bythe protrusion and the protrusion receiver is changed so thattheforce biasing the pinch roller againstthe platen is changed. That is, when the cam follower follows the first positioning cam surface portion, the paper pressing roller is resiliently biased againstthe platen, atthe same time the switch controlling the paperfeeding motor is deactuated, and the pinch roller is biased againstthe platen with a relatively strong biasing force. When the cam followerfollows the second positioning cam surface,the switch is actuated and the pinch roller is resiliently biased againstthe platen with a somewhat lesser biasing force. When the cam fol lowerfol lows the third positioning cam surface portion,the switch is maintained actuated and the pinch roller is resiliently urged againstthe platen with a relativelyweak biasing force.

The invention is illustrated, merely byway of example, in the accompanying drawings, in which:- Figures 1 to 3are cross-sectional views taken along a line 1-1 in Figure 7 to explain the operation of an embodimentof a paperfeeding mechanism according to the present invention for a printer; Figures 4to 6are cross-sectional views taken along 2 GB 2 182 287 A 2 a line IV-1V in Figure 7 of the paperfeeding mechanism of Figure 7; and Figure 7is a partially broken-away plan view of a paperfeeding mechanism according to the present 5 invention for a printer.

Referring specifically to Figures 1, 4 and 7 of the drawings, an embodiment of a paperfeeding mechanism according to the present invention for a printer has a platen 1 arranged to be rotated to feed recording paper P. A pinch roller 2 (Figure 4) is resiliently urged againstthe platen 1. The recording paper P isfed between the platen 1 and a pinch roller 2. Ashaft la of the platen 1 is rotatably supported in a platen bearing 3 (Figures 1 and 7) which is rotatably supported by a frame 4 of the printer. The platen bearing 3 is provided at its outward projecting end with a knob 5 fixed thereto and at its intermediate portion with a cam portion 31. A slot 31 a is formed in a side surface of the cam portion 31. The cam portion 31 has a cam surface including a first positioning cam surface portion 31b, a second positioning cam surface portion 31 cand a third positioning cam surface portion 31 d, these having different radii. The cam surfacefurther includes a switch operating cam surface portion 31 e. A paper pressing lever 6 is rotatably attached to a shaft7 provided on theframe 4. A paper pressing roller8a for applying frictionto the recording paper P is rotatably mounted on a shaft (Figure 7) which is supported at one end of the paper pressing lever 6. A connecting bar 10 is rotatably attached at one end to the other end of the paper pressing lever 6through a connecting pin 9. A pin 1 Oa projects from the other end of the connecting bar 10 and is inserted into the slot31 a to follow rotation of the cam portion 31. Atension spring 11 (Figure 7) extends between the paper pressing lever 6 and the frame 4 and a tension spring 12 extends between the connecting bar 10 and the frame 4. A switch 13 for a paperfeeding motor (not shown) is disposed under the cam portion 31 and is arranged to be turned on when an actuator member 13a of the switch 13 is depressed by the switch pressing cam surface portion 31 e. A stage portion 14 is arranged in the path of travel of the pin 1 Oa to lift an end portion of the connection bar 10. A support shaft 15 is disposed in parallel with the platen 1 and rotatably supported bythe frame 4. A lever 16 is fixed at one end to an end of the support shaft 15, so thatthe lever 16 can be pivoted about said one end. A rotatable cam follower 16a is provided on the other end of the lever 16 to followthe rotation of the cam portion 31 therebyto cause the lever 16 and the support shaft 15 to pivot and rotate respectively.

A support arm 17 is fixed to the support shaft 15 (Figure 7). The support arm 17 is integral with a boss portion 17a fitted on the support shaft 15, and is integrally provided at its tip with a connecting shaft 17b. A protrusion 17c is formed on the boss portion 17a (Figure 4). A spring hanger 17dis integrally formed on the support arm 17 at a position adjacent to the platen 1 and spaced by a slight distance from the protrusion 17c. A roller receiver 18 is connected with the support arm 17. The pinch roller 2 is rotatably supported at one end of the roller receiver 18, so as to be resiliently biased into contact with the platen 1. A connecting notch 18a is formed in the other end of the roller receiver 18 so that the connecting shaft 17b is rotatably and movably engaged with the connecting notch 18a. An upright bent portion 1 8b is respectively formed at each of the opposite sides of the roller receiver 18 and a concave protrusion receiver 18c is formed in the upright bent portion 18b so as to be engageable with the protrusion 17c. A spring hanger 18dis formed on the roller receiver 18 and a tension spring 19 is stretched between the spring hanger 18dand the spring hanger 17dof the support arm 17.

As shown in Figure 6, the support arm 17 pivots only within a predetermined angular range from a retracted position where the support arm is pivoted in a direction opposite to the roller receiver 18 to an advanced position (see Figure 4) wherethe support arm is pivoted toward the roller receiver 18 in responseto rotation of the support shaft 15 as a result of the lever 16 moving overthe cam portion 31. A knob 20 forturning the shaft 1 a of the platen 1 is fixed on an end of the shaft as seen in Figure 7.

When the knob 5 is turned counterclockwise after the recording paper P is inserted between the platen 1 and the pinch roller 2, the platen bearing 3 rotates counterclockwise, and the cam portion 31 rotates counterclockwise to causethe pin 10a located in the engaging portion of the slot 31 a as shown in Figure 1 to followthe cam portion 31 to reach the position shown in Figure 2. As the cam portion 31 rotates,the connecting bar 10 is moved by the pin 1 Oa, the paper pressing lever 6 is swung counterclockwise to raise the paper pressing roller shaft 8, and the paper pressing roller 8a is separated from the platen 1. In the position shown in Figure 2, an end portion of the connecting bar 10, where the pin 1 Oa is formed, is lifted by the stage portion 14 so as to cause the pin 1 Oa to separate from an engaging portion of the slot 31 a and enter a sliding portion. The pin 1 Oatherefore does notfollow subsequent rotation of the cam portion 31. Further, in the position of Figure 2, the switch pressing cam surface portion 31 e of the cam portion 31 presses down the actuator member 13a of the switch 13to close it so that the paperfeeding motor is started and the recording paper P is drawn in. After a predetermined period of time, afterthe leading edge of the recording paper P has passed in front of a reflection-type sensor (not shown),the paperfeeding motor is stopped and the recording paper P is set at a predetermined position.

As shown in Figure 1, when the cam follower 16a is in contactwith the first positioning cam surface portion 31b of the cam portion 31, the supportshaft 15 is in the position shown in Figure 4. At thattime, the support arm 17 is in its advance position and the roller receiver 18 is pushed forward to its advanced position bythe support arm 17 to the connecting shaft 17b thereof, so thatthe protrusion 17cand the protrusion receiver 18c are separated from each otherto extend the tension spring 19. Accordingly, the connecting shaft 17b and the connecting notch 18a forms a fulcrum for the movement of the pinch roller 2 and this fulcrum is separated from the line of action of the spring force of the spring 19 (that is, a line connecting the spring hangers 17dand 18d), so z 3 GB 2 182 287 A 3 11 that the pinch ro I I er 2 is reshientlyurged against the platen 1 with a relatively strong biasing force.

As shown in Figure 2, when the cam follower 16a is resit iently urged against the second positioning cam surface portion 31 c, the support shaft 15 rotates a little counterclockwise from the position shown in Figure 4 to the position shown in Figure 5.Atthat time, the connecting shaft 17b and the connecting notch 18a are retracted a I ittlefro m the position shown in Fig ure4 and the pinch roller 2 is also 75 retracted a I ittle. However, the protrusion 17c and the protrusion receiver 18c are separated a I ittlefrom each other, so that the spring force of the spring 19 is exerted onto the platen 1 through the pinch roller 2 through the a bove-mentioned fulcrum thereby resi I iently to urge the pinch rol I er 2 ag a instthe platen 1 with a sufficiently large biasing force which is slightly less than that in the position shown in Figure 4.

As described above, the recording paper Pis 85 inserted between the platen land the pinch roller 2 in the position as shown in Figures 2 and 5. In the case where the recording paper is drawn in misaligned, for example, at an angle, the knob 5 is further turned counterclockwise so as to correct the a I ignment of the recording paper. When the cam portion 31 comes to the position shown in Figure 3, the connecting bar 10 does not move together with the cam portion 31 because the pin 1 Oa slides in the sliding portion of the slot31a, so that the position of the paper pressing lever6 is not altered. Becausethe cam follower 16a is resiliently urged againstthe third positioning cam surface portion 31 dhowever, the support shaft 15 rotates furthercounterclockwiseto the position shown in Figure 6. Atthattime, the support arm 17 is in the retracted position and the protrusion receiver 18c is engaged with the protrusion 17c underthe action of the spring force of the spring 19 and the roller receiver 18 is maintained with the engaging position as a fulcrum. Because the fulcrum atthat time is extremely nearto the line of action of the spring force of the spring 19, the pinch roller 2 is resiliently urged againstthe platen 1 with a relatively weak biasing force. In that position,the pinch roller2 is more retracted than in the position shown in Figure 5. Accordingly, if the knob 5 is turned,the state shown in Figure 5 is changed to that shown in Figure 6 and then misalignment of the recording paper P can be corrected so thatthe recording paper having a correct alignment can be sandwiched betweenthe platen 1 and the pinch roller 2. Even in thestate shown in Figures 3 and 6,the switch 13 is closed, and therefore if the state is turned backto the state shown in Figures 2 and 5to increasethe biasing force acting on the pinch roller, the recording paper P in the correct alignment can be fed to a predetermined position by operation of the paperfeeding motor.

When printing is performed afterthe recording paper P has been set, the state is returned backtothe state shown in Figures 1 and 4,where the paper pressing lever 6 is returned into its original position, the paper pressing roller 8a is resiliently urged againstthe platen 1 with the recording paper P sandwiched therebetween, and the pinch roller2 is also resiliently urged againstthe platen 1 by a large biasing forcewith the recording paper P sandwiched therebetween, so thatthe recording paper P is frictionallyfed bythe paperfeeding motorduring. printing.

When the recording paper P is printed usingtractor feeding, if the state is brought into that shown in Figures 3 and 6, the pinch roller 2 is resiliently urged againstthe platen 1 with a relatively weak biasing force with the recording paper P sandwiched therebetween, so that appropriate tensileforce is applied to the recording paper so that clear printing is possible.

In the above described paperfeeding mechanism according to the present invention, only byturning the knob connected with the platen bearing isthe paper pressing rollerseparated from the platen and atthe sametimethe switch of the paperfeeding motorforfeeding the recording paper is turned on, so thatthe recording paper can be automatically drawn in with a simplified structure as well as an improved reliability of operation. When the recording paper is drawn in a misaligned manner, merely by further turning the knob,the biasing force acting on the pinch roller is reduced and the recording papercan be surely inserted in correct alignment between the platen and the pinch roller, thereby ensuring correct automatic insertion of the recording paper. Further, when the recording paper is tractorfeed, an appropriate and relativelyweak biasing force is applied to the pinch rollerfor urging the pinch roller againstthe platen, so that an appropriate tensile force can be maintained on the recording paperto effect clear printing.

Claims

1. A paper feeding mechanism fora printer comprising: a platen forfeeding recording paper; a pinch roller resiliently urged into contactwith said platen; a platen bearing for rotatably supporting said platen, said platen bearing being arranged to be rotatable by a knob f ixed to a outward projecting end of said platen bearing; a cam portion on the platen bearing; a rotatable paper pressing leversupporting a paper pressing roller; a connecting leverfor pivoting said paper pressing lever in responseto rotation of said cam surface; a cam follower lever fixed on a rotatable support shaft and provided at one end with a cam follower engageablewith a cam surface of said cam portion; a support cam fixed on said supportshaft so as to be pivotally displaced in responseto rotation of said support shaft; a roller receiver carrying said pinch roller atone end thereof; connecting meansfor rotatably and movably connecting one end of said support arm andthe otherend of said roller receiver; a spring extending between said support arm and said roller receiver; and a protrusion and a protrusion receiver provided on one and the other of said support arm and said roller receiver, said protrusion and said protrusion receiver being disposed at a position separated from a line of action of a spring force of said spring, said cam surface of said cam portion including a first, a second and a third positioning cam surface portions of different radii, said first, second and third 4 GB 2 182 287 A 4 positioning cam surface portions being, in operation, selectiveiyfollowed by said cam followerfor displacing said cam follower lever into a selected one of three rotational positions, said cam surface further including a switch pressing cam surface portion for operating a switch controlling a paperfeeding motor.

2. A paperfeeding mechanism as claimed in claim 1 in which said protrusion is provided on the support arm and the protrusion receiver is provided on the roller receiver.

3. Apaperfeeding mechanism as claimed in claim 1 or2 in which the spring extending between said support arm and said roller receiver is a tension spring.

4. A paper feeding mechanism fora printer substantially as herein described with referenceto and as shown in the accompanying drawings.

5. Any novel integer orstep, or combination of integers or steps, herein before described a nd/o r as shown in the accompanying drawings, irrespective of whetherthe present claim is within the scope of or relatesto the same or a different invention from that of, the preceding claims.

6. Apaperfeeding mechanism fora printer comprising: a platen driven to rotate in feeding of a paper; a pinch roller urged so as to resiliently contact with said platen; a platen bearing for rotatably supporting said platen, said platen bearing being arranged to be rotatable byturning a knobfixed to an outward projecting end of said platen bearing, and having a cam portion; a rotable paper pressing lever for supporting a paper pressing roller; a connecting leverfor swingingly driving said paper pressing lever in responseto rotation of said cam portion; a cam follower leverfixed on a rotatable supportshaftand provided at its end portion with a cam follower engageable with a cam surface of said cam portion; a support arm fixed on said support shaft so as to be swingingly displaced in response to rotation of said support shaft; a roller receiverfor bearing said pinch roller at one end portion thereof; connecting means for rotatably and movably connecting one end portion of said support arm and the other end portion of said roller receiver; a tension spring stretched between said support arm and said roller receiver; and a protrusion and a protrusion receiver provided on one and the other of said support arm and said roller receiver respectively, said protrusion and said protrusion receiver being disposed at a position slightly separated from a line of action of a spring force of said tension spring toward said connecting means; said cam surface of said cam portion including a first, a second and a third positioning cam surface portions which are different in radii from each other, said first, second and third positioning cam surface portions being selectively followed by said cam followerfor displacing said cam follower lever into selected one of three rotational position, said cam surface further including a switch pressing cam surface portion for turning on/off a switch of a paperfeeding motor.

Printed for Her Majesty's Stationery Office by Croydon Printing Company (UK) Ltd,3187, D8991685. Published by The Patent Office, 25 Southampton Buildings, London, WC2A lAYfrom which copies maybe obtained.

hp